1. Field of the Invention
Aspects of the present invention relate to an image scanning apparatus and an image scanning method thereof, and more particularly, to an image scanning apparatus configured to accurately detect a leading edge and a tail edge of a document to be scanned, such as a manuscript, and calibrate leading and tail margins of the document.
2. Description of the Related Art
Generally, an image scanning apparatus illuminates light on a document to be scanned and scans an image formed on the document. By way of example, the image scanning apparatus includes a scanner, a facsimile, and a multi-functional printer having a scanning unit.
Image scanning apparatuses are classified into three types according to what is moved in order to scan the document: a flat-bed type image scanner, a sheet-feed type image scanner, and a hybrid type image scanner. A scanning unit of the scanner is moved in the flat-bed type image scanner, and a document is moved in the sheet-feed type image scanner. The hybrid type image scanner is similar to a sheet-feed type image scanner and is generally a flat-bed type image scanner having an auto document feeder (ADF) attached thereto to supply sheets to the scanner. Here, the scanner illuminates light on the document and scans a visible image formed on the document in the form of an optical signal, converts the scanned optical signal into an electric signal, and provides the electric signal to a signal processing module.
In performing an image scanning operation with respect to documents continuously fed by use of the document feeder, both the sheet-feed type image scanner and the hybrid image scanner detect the entrance of each document, the leading edge, and the tail edge of the document.
Accordingly, the conventional image scanning apparatus includes a first detector and a second detector disposed along a document feeding path of the document feeder. The first detector senses entrance of the document, and the first detector comprises a first actuator installed reciprocally and rotatably along the document feeding path, the first actuator being rotatable between a first position, when no document has entered the document feeding path, and a second position, when a document has entered the document feeding path. The first detector further comprises a first sensor to turn on or off according to the position of the first actuator. The second detector detects the leading and the tail edges of the document, and the second detector comprises a second actuator provided on the document feeding path between the first detector and a document scanning position, and a second sensor turning on or off according to the position of the second actuator. The second actuator is installed reciprocally and rotatably between a first position, when no document has entered a portion of the document feeding path at which the second actuator is disposed, and a second position, when a document has entered the portion of the document feeding path at which the second actuator is disposed.
Accordingly, the conventional image scanning apparatus calculates a start position and an end position of an image scanning operation according to on/off points of the second sensor, a distance between a detecting position and a scanning position, and the feeding speed of the document.
In the conventional image scanning apparatus, the second actuator contacts the fed document and is then rotated. Thus, a chattering phenomenon may be caused by a mechanical vibrating of the second actuator when the document and the second actuator contact each other. In addition, there may be a difference in time between when the document contacts the second actuator and when the second actuator rotates. Thus, errors may be caused between on/off points of the second sensor and the detection of the leading and the tail edges of the document.
Further, as the detecting positions of the leading and the tail edges of the document and the scanning position of the document are different in the conventional image scanning apparatus, it is not possible to detect the accurate positions of the leading and the tail edges of the document where the feeding speed of the document is not accurate. Moreover, the rotation direction of the second actuator when the second sensor turns on or off is opposite to the second sensor, and thus, the point of time when the second sensor turns on and the point of time when the second sensor turns off become different, thereby causing an error in the margins of the leading and the tail edges of the document.